Process of synthesizing hydrocarbons



July 8, 1952 c. w. MONTGOMERY ErAL 2,502,810

PROCESS oF sYNTHEsIzING HYDRocARBoNs Filed June 2, 1949 Patented July 8, 17952 PRooEssjoF sYrHEslzING ,v Y 'HYDnooARBoNs Charles WVMontgomery and William A'. Horne, v Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Application June 2, 1949, Serial No. 96,659

This invention relates to Ythe production of h-ydrocarbons by the reaction between hydrogen and carbon monoxide. Moreparticularly, the invention relates to a process for :the production ofv hydrocarbons from hydrogen and f carbon monoxide utilizing a fixed catalyst bed. Y

In the production of hydrocarbons,e..g., hydrocarbons containing rthree or more carbon "atoms, such as hydrocarbons boiling within the gasoline and gas oil boiling ranges, .and wax hydrocarbons, by meansof the reaction between hydrogen and carbon monoxide the problems-'presented arise because of thehighly exothermic nature of the reactionand because of the necessity of maintaining long catalyst life if economical operation is to be obtained. As a solution to the problem of temperature control, a reactor has been employed comprising a plurality of catalyst tubes of relatively small 'cross-sectional area anda surrounding chamber containinga liquid cooling medium. This is notan entirely satisfactory solution to the problem because of the high initial cost of theequipment and the high vmaintenance costs which arefespecially serious when catalyst change becomes necessary; It has also been proposed to carry `out the reaction on the adiabatic principle using-a fixed bed of catalyst and recycling a portion of the product gases. vThe proposals along this line that have been made, however, have suggested the-recycling of Van uneconomical amount of gas or the use cfa v2 to 5 per cent of the operating time of the system, depending' upon the effectiveness of the process employed. We have found that an important factor affecting catalyst life is the composition of the mixture charged to the reactor.

We have discovered in accordance with the invention that long catalyst life -can beobtained while producing good yields of the desiredhydrocarbons in relatively simple equipment by carrying out the reaction between hydrogenand ca rbon monoxide as described'below. Theprocess'of the invention is 4carried out on the adiabatic 11 claims. (c1. 26o-449.6)

principle so that Acontrol of the temperature of -the catalyst is .effected by the kcomposition and quantity of gases contactedwth the catalyst. The preferred embodiment comprises passing into contact with an ironsynthesis vcatalyst maintained inaxed bed at a hydrocarbon synthesis temperature and at a superatmospheric pressure a lgas mixture consisting'of a combination of about 1 vpart by volume of ,a feed gas consisting essentially of hydrogen and carbon monoxideyin a mol ratio. of at least 2.511, preferably` atleast 2.8:1; for examplebetween about 2.8:1 and-1:1, and especially between about 2.9:1 to 3.2:1,fand about -8 Yto about v15.parts by .volumegof gas recycled from the. products ofthe reaction. The

process is carried out" so that ,the combination of the feedgas'and the-recycled gas contains hydrogen and carbon monoxide in a mol ratio of at least 15:1 and preferably between about 15:1 and 30:1. The hot products of reaction are then cooled to condense at least the normally liquid hydrocarbons and other compounds boiling above such hydrocarbons. Preferably.. the condensation is carried outzso as to condense most of the Cifand. heavier hydrocarbons andV oxygenated o compounds formed in the reaction. The ,remainder of .the reaction products in `gas phase under these conditions is separated into a portion for. recycling and a portion which is removed from the system. The recycled portion isthen admixed with fresh feedgas, preferably heated to about the` temperature required .for'initiation Vof the desiredv reaction, and passed into contact with the catalyst. f

The process ofthe inventionshould be carried out so as to obtain high conversions of carbon monoxide: preferablyY atleast v98 per-cent, and ordinarily a'run should be stopped when the conversion has'fallen to'below 95 per cent. High conversions are important because any ,carbon monoxide that is not converted to useful products in a process of this ytype cannot berecovered effectively. l, With given temperature and pressure conditions and catalyst activity, the conversion ofcarbon monoxide is determined principally by the reactor.feedfcomposition and the space velocity maintained. The `control of. tem;- perature in the present process-is accomplished by controlling the temperature and composition of thereactor feed. We have-discovered that `when operating as described involving theuse of 3 catalyst bed; for example, a temperature gradient of about 100 to 200 F., and preferably a temperature gradient of about 125 to 165 F. We have found that under these conditions the yield of the desired products is high and the process is made commercially attractive because extended runs can be carried out and low ratios of recycled gas to fresh feed can be employed. The use of high ratios of hydrogen to carbon monoxide `in the fresh feed and in the reactor feed, however, is essential since the temperature at the exit of the catalyst bed is necessarily high, which we have found to cause, when the reactor feed contains a high proportion of carbon monoxide, early destruction of desired physical properties of the catalyst. In general, it is preferred to operate so that the temperature of the reactor feed is at, or not substantially above, the reaction initiation temperature and the temperature at the exit end of the catalyst bed is between about 610 to about 630 F. Depending on the iron catalyst employed and its activity, the minimum reactor feed temperature should lie within the range of about 430 F. to about 525 F.

By operating as described, the catalyst can remain on stream for an extended time and it may -be subjected to a plurality of regeneration and ori-stream periods. The process is characterized by effective utilization of carbon monoxide, which as stated above, is substantially entirely converted to useful products in the synthesis reaction. The gas which must be removed from the process contains 'any amount of hydrogen making this gas available for employment in hydrogenation reactions. Moreover, by operating in this way a morevcr less balanced yield of gasoline hydrocarbons. gas-oil hydrocarbons and Wax hydrocarbons -can be obtained.

A typical method of carrying out the preferred embodiment will be described in connection with theA accompanying drawing in which the single figure is a simplified flow sheet of a suitable plant system. Referring to the drawing, the fresh feed, comprising Vin this case hydrogen and carbon monoxide in a mol ratio between about 2.9:1i: and about 3.211, is fed into the system under pressure at a controlled rate through a valved line -I which leads to a line 2 in which is flowing recycled gases as will later be described. The refcycled gases will comprise, in addition to butane,

propane, ethane, methane, and the corresponding vunsaturated hydrocarbons; oxygenated organic compounds; carbon monoxide; hydrogen; carbon dioxide; and normally a small amount of nitrogen. These gases will be saturated with water vapor and the Yproportions in which the Vseveral compounds are present in the recycled gases will depend upon the specific conditions employed in separating the gases for recycling from the product gases. Also, because the sepa- 'ration' is not clean-cut there will be traces of heavier hydrocarbons. The mixture of feed gas and the recycled gases passes through a gas heater -3 wherein the temperature of the gases is preferably raised to the temperature maintained at the top of the catalyst bed, for example, a temperature between about 430 and 500 F. The

gases at this temperature are passed from the gas in the reaction, running away of the temperature of the catalyst bed is prevented. However, under the conditions described there is an increase of temperature from top to bottom of the bed of about 125 to about 175 F., provided however that the maximum temperature reached does not exceed about 630 F. Thus the temperature at the bottom of the bedY may lie within the range of about 600 to 630 F.

The product gases are removed from the bottom of the reactor through a line I0 and are passed through a heat exchanger II. This heat exchanger is preferably employed for the production of steam and for this purpose is shown connected with a steam drum I 2 by means of lines I3 and I4. The reaction products, somewhat reduced in temperature, are then passed through lines I5 and I6 and are then cooled additionally in a cooler I'I in which their temperature is reduced to at least F., for example to a temperature between about 40 and about 120 F., the specific temperature being sufficiently low to cause condensation of the desired products. The cooled products are then passed through line I8 leading to a separator I9Uof conventional design. In this separator an aqueous layer and a liquid hydrocarbon layer are formed. The hydrocarbons that are liquid under these conditions are removed fromthe system through a line 20 and the aqueous layer comprising a solution of Aoxygenated compounds, such as alcohols and ketones, is removed through line2 I. The remaining gaseous products are passed from the separator through line 22 and a portion of them is vented from the system through line 23. The vent gas may be processed to separate the hydrocarbons and hydrogen. The portion vented is regulated to hold system pressure, in this case pounds per square inch and acts as a bleed to prevent inert gas build-up in the system. When a run is in progress, the amount of vent gas plus liquid products will be equal in Weight to the feed gas. The remaining gases are passed through line 24 and are raised to a pressure somewhat inexcess of the desired reaction pressure by means of blower 25 so `that the volume of gases recycled to the reactor is about 8 to 154 times the volume of the fresh feed, .id then flow into line 2 as previously described.

In many cases the catalyst is subjectedto partial or complete reduction prior to being contacted with the reactor feed. This may be accomplished in the system shown by introducing hydrogen through line I, raising the temperature of the hydrogen in heater 3 to a temperature. for example, of the order of 600 to 950 F. and then passing the heated gas through the reactor. .The gases produced in this reducing procedure may be removed vfrom the system through line IIJ4 and line 21, the valve in line I6, of course, being closed. Regeneration of the catalyst by oxidation with an oxygen-containing gas such as air can be accomplished rin the system shown by introducing air through line 28 and passingthe air through line ageeasio suitable promoters such as alumina vandvpota'ssium oxide .andfmay lbe disposed on fsuitable supports such vasu fullersj earth, activated` alumina, acidtreatedamontmorillonite clays and the like. .A The research work carried out in connection with this invention, however, has indicated that iron catalysts prepared by precipitation of iron :oxide are particularly valuable, especially when employed Y in the unpromoted state. We have also found that the extent of reduction of these catalysts has an important effect upon their value in the process. Thus, superior results are obtained when the catalyst has been from to 100per cent reduced from the oxide and preferably from 50 vto 100 per cent reduced from the oxide. extent of the reduction of the catalyst is felt most strongly during the period when the unit is being placed on stream although this extent of reduction also has an important effect on the character rThe effect of the height; The reactor. was part of as'ystem' such a'sdisclosedin the drawing;V 'The reactor was des signed for.. adiabatic operationsince it consisted simply of the reactor shell, the bottom foraminous catalyst. support, andmeans forpreventingheat loss from the catalyst bed to the atmosphere.`

The catalyst .Was then dried, for example; 'by passing a gasoverthe catalyst at a temperature of about 250 EttoBOO" F. for about 3 hours. Hydrogen was; :usedVA as y theV fdrying ,gas 1. for convenience; however, aninertgas is suitable butrequiresflushing from the i'systemaften drying. :At this Stage theV catalyst :Wasi ready; for ,use when it was to;be usedas the oxide'.` .When-completel'y or partially reduced catalysts were to be prepared, heated hydrogen gas was then flowed over the catalyst atoneatmosphere pressure at a space velocity of about 1150. When the catalyst bed had been heated to a temperature of about 510 F., reduction of the catalyst began to occur. The

passage of the heated hydrogen in contact with the catalyst was continued until the desired degree of.:V reduction had-been attained; the catalystreaching a temperature in the neighborhood of 650 F. early in the reduction period. For

' example, to prepare a catalyst about 50 per cent ofthe products obtained. In this connection, itV

will be understood that `the catalyst will usually be reduced in the synthesis unit and therefore in speaking of extent o f reduction, the extent of reduction of the mass of catalyst in the unit as determined as hereinafter described or by similar methods, is intended. y

As previously indicated, if themaximum temperature is. controlled, excellent results are obtained in .the presentfprocessrfby maintaining a substantial temperature gradient across thecatalyst bed. When maintainingy the mol' ratio of hydrogento carbon monoxide inthe freshvfeed within'the ranges previously described and utiliz# ing a partially reduced iron. oxide catalyst, the temperature of: the charge mixture may be of thel order of 430 to- 450 F. At this temperature the desired reaction is initiated and with ratios of recycled gasesto fresh feed of about 8:1 to about :1, the maximum temperature in the catalyst bed, .which is reached'atthe .exit of the-bed, is about 600 F. to about 630 F. On the-other hand, when using an oxide catalyst,it is necesd sarythat the mixture be heated toa vtemperature ofthe orderof500 F. in order to initiate reaction. In this'case :the recycle `ratio must be .increased within the limits mentioned above in order not-to exceed a maximum temperatures/ff about 630 F. It will be understood that the effect of an excessive temperature in the catalyst bed is to promote the formationv anddeposition on thecatalfystof relatively I-large amounts of carbon which' cause the rapid destruction of the physical state-ofthe catalysurequiring an early shutdown of the unit. There will now be described a number of runs further illustrating the present invention. 'The catalysts employed inthese. runsfwere modifica` tions' of the same base catalyst. v The base catalyst was prepared as a precipitated 'iron oxide which analysis indicated to be FezOa Withsonly traces of other metals. The catalyst Ahadlbeen formed-in a compression pelleting machine 'intocylindrical pellets about 1/8 inch in diameter and about 1A; inchheight. v In each-case 1400 cc. of this .catalyst weighing about 2734 grams lwere charged to a Vreaotorabout 3 inches in? diameter forminga xed catalyst bed about 11 inches in reduced from the oxide, the passage of hydrogen was rcontinued for about twenty-four hours. 490.9 grams of Water'were formed in the reduction procedure. lSince complete reduction of the catalyst would have formed 922.7 grams of Water, the catalyst was 53.2 per cent reduced from the oxide. v

f .The procedureju'st described was followed not generated.

To place the reactor on stream it;was brought up toa pressure-of about pounds per square inch with hydrogen, and at this pressure recycling Was started at about 285. cubic feetuper hour v(at standar-:l conditions of 32 F. and one atmosphere pressure). The catalyst bed temperature was brought up to about the temperature requiredfor initiationi of .thereactiom the specific temperatures beingV givenin the folloWingTable I. At

that time the flow of a fresh feed-synthesis gas composed substantially entirely of hydrogen and carbon monoxide in a mol'ratio of hydrogen to carbon monoxide ,of .about 3.221v into the reactor was begun at arate of about'18.5 cubic feet per hour (at standard conditions of 32 F'. and-cheatmosphere 1 pressure) in combination with; hy.- drogenin an amount-,sufficient tomakethetotal flow about 360 cubic feet per hour. -The rate of flowoffreshfeed was increased in stages while decreasing 1 the;A amountfof hydrogen untilk it reached a va'lue'of about 32.5:cubic feet-per hour. rlhis isa space velocity (volumes ofv gas at stand-e ard conditions per volume ofcatalyst .per hour) of .about 657. The time required Vto reach this value depended upon' the*speciccat'alystv used. During this start-up or lining-out period,` the gases are separated as described below and adjusted in y'volume 4in relation to the fresh feed and hydrogen to obtain the desired maximum *temi peratuie and v temperature gradient across the catalystfbed.l l v At the end of this liningLout period,the fresh feed in 'admixture with recycled vgases was being introduced Y at the reaction initiation? tempera-l ture andthe maximum temperature inf the cat'- alyst bed which existed at about the bottom'of the-bed was in each case as shown in* Tablev I. The 'reaction products produced were cooled l to 7 about 40 F. While maintaining the pressure in the neighborhood of 150 pounds per square inch, and were passed into a separator wherein a separation of the liquid and gaseous materials was when operating outside the invention, data with respect to two periods of operation on each ot two catalysts are given in the following table as Well as data with respect to single periods of accomplished. The gaseous products were sep- '5 operation on each of three other catalysts. Two arated into a portion which was vented from the of these three catalysts were not used under consystem and a portion equal in volume at standditions outside the scope of this invention, while ard conditions to the multiple of the volume of the third was not used under the conditions of the fresh feed indicated by the recycle ratio shown the present invention. Of the catalysts identiin the table. The inlet temperature was in- 1o fied in the table, catalyst A was 53.2 per cent creased slightly as a run progressed in order to counteract the decrease in carbon monoxide conversion caused by reduction of catalyst activity. The run was continued so long as the condireduced from` the oxide, catalyst B was 71.5 per cent reduced, catalyst C was 90.8 per cent reduced, catalyst D was 10.9 per cent reduced, and catalyst E was an unreduced oxide.

Table I Catalyst C D E Period I Period II Period I Period II Space Velocity-Fresh Feed 657 657 657 657 657 657 657 Mol Ratio lh/C in Fresh Feed 3.29 3. 19 3. 26 3. 26 3. 19 3 26 3. 27 Recycle Ratio (Vol. of Recycled G Fresh Feed) 9.0 9.1 9.1 9. 1 9, 1 9. 1 24. 9 Space Velocity-Reactor Feed. 6. 550 6, 640 6, 600 6, 600 6, 636 6, 661 16, 850 Mol Ratio Hz/ C O in Reactor Feed- 24. 8.3 22. 9 11.4 18. 7 19. 6 18.4 C0 Conversion (percent) 99. 5 85. 1 99. 7 96. 6 9B. 5 99. 3 9B. 5 Liquid Yield (CH Per 1000 Cubic Feet Fresh Feed) in poun 5. 4 3. 5 5. 13 3. 53 5. 62 5. 2 3. 3 C Efficiency (percent converted CO converted to 03+ Hydrocarbons) 75. 4 65. 5 70. 6 58. 6 76. 5 69. 2 45. 4 05+ Eiiiciency (percent converted CO converted to C Hydrocarbons) 53. 5 46. 9 45. 2 37. 5 52. 7 44.8 24. 5 Gasoline (Cr-400 F.) Octa Res.) Clear 54 48 56. 6 38. 7 58. l 46.1 47. 4

+306. Tel./G 76.8 66.9 78.4 72 73.1 73.4 65.4 Inlet Temperature F 439 452 455 466 447 459 551 Maximum Catalyst Bed Temperature F 599 615 599 606 609 009 Temperature Gradient Across Catalyst Bed F 160 163 144 140 159 150 58 Relative Power Requirement to Recycle Gas (Recycle Ratio of 9.0= 100) 100 102. 2 102. 2 102. 2 102. 2 102. 2 769 tions of operation described previosly were maintained. The most striking indication of unsatisfactory operation is the drop in the mol ratio of hydrogen to carbon monoxide in the reactor feed to below :1, caused by reduction in catalyst activity. The on-stream period was then discontinued.

'I'he catalyst was then regenerated by a procedure comprising flushing the system with an inert gas and then bleeding into the reactor a small stream of air (about 3.5 cubic feet per hour) and a stream of nitrogen (about 9.9 cubic feet per hour). The products of the regeneration were recycled to the catalyst bed at a rate of about 80 to 85 cubic feet per hour. The peak catalyst bed temperature was about 450 F. under these The results given in Table I provide striking evidence of the advantages of the process of the invention involving the use of high hydrogen to carbon monoxide ratios in the fresh feed, preferred recycle ratios of about 9 and maintaining the hydrogen to carbon monoxide ratio above 15:1. It is to be noted that these advantages reside not only in the improved liquid yields and proportion of the converted carbon monoxide appearing in the form of relatively heavy hydrocarbons, but also in the quality of the gasoline produced. This last advantage is unexpected in that in most processes where high yields are obtained it is usually the case that quality suffers.

If the results obtained using catalyst A in period I are compared with results obtained using conditions. The air rate was then gradually inthis catalyst in period II, it will be seen that the creased to about 23 cubic feet per hour and the 55 conditions maintained in these two periods are nitrogen feed cut to zero. The peak temperasubstantially the same except that the hydrogen ture of the catalyst was gradually increased to to carbon monoxide ratio in the reactor feed in about 950 F. where it Was maintained throughperiod I was 24.5 whereas this ratio in period II out most of the regeneration period which usually was 8.3. Also the carbon monoxide conversion occupied a total time of about 36 hours. The re- 60 was 99.5 per cent in period I and 85.1 percent generated catalyst after successive on-stream pein period II. These differences in operating conriods was in substantially the same condition as ditions resulted in a. marked decrease in liquid the fresh base catalyst introduced into the reyield, the yield in period 1I being only about 65 actor. per cent of the yield in period I. Moreover, the

The cycle of operations in the present process Ca+ and C5+ eiiciencies for period I are substancomprises the periods described; aperiod for drytially better than those for period II and the ing and reduction of the catalyst, if a completely quality of the gasoline is substantially better for or partially reduced catalyst is used; a lining-out period I. A similar comparison may be made period; a reaction period; and a regeneration between catalyst B, period I, and catalyst B, period. The lining-out period and the reaction period II. In this case the only substantial difperiod, during both of which hydrocarbons are ference in operating conditions is the hydrogen produced, are together referred to as the onto carbon monoxide mol ratio in the reactor feed: stream period. 22.9 as compared with 11.4. Yet the liquid yield,

In order to compare results obtained when C3+ and 05+ efliciencies, and the quality of the operating in accordance with the invention and gasoline were all markedly better for period I -fected by varying conditions in accordance with than for period 1I. Therun on catalyst E, which Ywas carried out under conditions outside the scope Aof thefpresent invention, are interesting in that the most important variation from therconditions .1'0 to compensate for decreased catalyst activity and' if such anxincrease in temperature is noteffective to raise the reactor feed hydrogen to carbon monoxide ratio above 15, then 'the lori-.stream of the invention resides in the recycle'ra-timwhich 2'5 period should bediscontinued=and the'lcatalyst is24 .9 ratherthan between about Slandabout 15. regenerated or replaced.v Withgajxedfee'dgas I-Iere again the liquid yield, efficiencies and qua-1 composition andjrecycle ratio,'tli'e compositionof ity of' gasoline were ally relatively low; A1Itis the reactor feed is dependent upon the-compostlb'elieved'that to some extent the disadvantageous tion 'of the recycled gases; Typical analyses vof results obtained -in this run are attributable-:to recycled gases (on dry basis). are-given Vin the 1 the 'fact vthat the catalyst was a completely oxifollowing Table II with respect to the run'invo'lvdized catalyst. As previously indicated, the ing the use of catalyst A in period I and period experimental work leading to the development vII, as to which other data was supplied 1in off this invention has indicated that partially or Table I. Y Y

' Table II (Sgfnggrlctt) co H. co. N. ont 01H. 02H1 Cant 01H8 04H1 one, dem 01H11 ou@ Perio 1I 0.5 67.1 40.7 1.0 15.8- 0.3 0.5 1.o a3v 1.1 1.0 0.3v 0.3 f0.4

Catalyst A, v

v remain.; 7.7 70.0 4.8 Y 1.1 10.1.1A 0.3 2.2 0.5 1.0 0.5 0.4 0.2 0.2 k- :01a

vcompletely reduced iron catalysts are superior 05 It has been stated 'previously that'thepreset for use in the present process to oxide catalysts f process has the advantage that the catalyst can and that catalysts which are to 100 per cent remain in use for anextendedperiod offtime. reduced from the oxide are especially preferred. The data given in the following Table III is of While thiscannot be shown by means of numeriinterest on this point. A run was terminated cal results, the run vcarried out in catalyst E had no when the pressure drop through the catalyst the additional disadvantage over those shown by o 'bed became excessive, indicating break-down of the' data in the table of being diicult to start up. catalyst, or the` run had been carriedout fa The temperature was difficult to control-and the Vsuficiently long time to demonstratef'thatit lining-out period was longer than was necessary could be continued indenitely. f v- Table III Total Tota Hom? on APcrrissssleagll-ggt Condition of Catalyst @mi aan ...saetta Blogg-ggg) En@ 11m1- cataiystA 890 143 0.15 Good. f Catalyst B. 1, 370 285 0.0 Good; slight amount oi powdering'. Catalyst C... 1,865 315 0. 0+ Reducedstate; 'some carbomwax, powder. Catalyst D... 1,221 100 0.0+ Good; slightamunt'of y powdering z Catalyst E 581 124 0.5 Fair bonditi0n; sorn'e Catalyst F 3".. 357 s 1 85 l 9.1 Pgir olonditiom .r Lncih plug'at basco( 1 No reduction time.

3 End 0f 357 3 Catalyst F was an iron oxide lyst F was carried out using a fresh feed containing hydrogen to carbon monoxide in amol ratio oi 1.8511, a recycle ratio of about 30, and a reactor feed containing hydrogen and carbon monoxide in a mol ratio oi 1.52zl. 1

.with the other catalysts. Also the run carried out using catalyst D, which was about 10 per cent vreduced from the oxide, created more difficulties .composition of the fresh feed, the composition of the recycled gases and the recycle ratio. Accordingly, the control of the process` can be efthe changes inthe mol ratio of hydrogen to carbon monoxide in the reactor feed. Forexample, when operating with a xed fresh feed composition and recycle ratio and this mol ratio falls below 15,` the inlet temperature should be raised The present process when carried out under Voptimumconditions is productive of hydrocarbons ranging from light gases throughV gasoline hydrocarbons to heavier liquid hydrocarbons and wax hydrocarbons. tribution aniongthe compounds included gin: the liquid yield (Ca+ hydrocarbons) is 'that for period I of the run on catalyst A. In this casetl'ie distribution, in weight per cent of the product, was: gas, 4.8 per cent; gasoline (Cs's to 400 F.);`` 69.9 per cent; 400-700 F., 18.7 per cent; and "above 700 F., 6.6 per cent. v

It will be understood that the conditions disclosed with respect to the foregoingrun's may be varied within the `scope of the invention. iWhile it is generallyprefered to carry out the process at a pressure of about vpoundsper square inch, other superatmosphcric pressures may-'be used, such as pressures withinr the ranges of about 50 to about 650 pounds per square inch. Since the pressure does not appearv Vto havea Typical of Y the product dis- `maintained within the klimits described above,

the'fresh feedfspaco velocity may be varied, the only considerations being ythe'f'practical'onesV of overcoming' pressure drop through the catalyst bed when high space velocities are employed. and of. an economical throughput at .lower space velocities..

' We' have stated that the reactorfeed should be heated prior to being Acontacted with the catalyst at least to the reaction initiation temperature, which varies depending upon the specific catalyst employed and the activity of the catalyst. We have also stated that the process can be carried out so as to compensate for a decrease in activity .of the catalyst by increasing the temperature during an on-stream period. While hydrocarcan be produced under other temperature "conditions, in general we prefer to maintain this reactor feed or inlet temperature when using a partially or completely reduced iron catalyst ywithin the range of about 430 to. about 475 F., the lower temperatures being employed when the catalyst is relatively fresh, either a new catalyst .ory regenerated catalyst, and the temperature being gradually increased towards the latter part vof a run. `When usin-g an iron oxide catalyst We have`V foundthat ordinarily reaction is not initiated unless the reactor feed is heated at least to about 490 F., and better about 500 F. During a run this temperature is preferably increased but the maximum should not ordinarily exceed about 530 F.

Y The prior description has largely been concernedwith a preferred embodiment of the invention involving condensing a part of the re- *action products and r-ecycling to the reactor'a portion of the remainder. The invention in its broader aspects is not limited to this embodiment .axs insofar as what-takes place in the reactor is concerned the vsource of the gases admixed with ,the fresh feed is unimportant and therefore gases which do not interfere with the reaction and -which provide hydrogen and carbon monoxide to the total reactor feed in amounts sufficient to .produce a total feed containing hydrogen and carbon monoxide in a mol ratio of at least 15:1

canbe employed in quantities such that the added' gases are present in amounts that produce a 'total' feed in which the volume ratio of added .gases to fresh feed is between about 8:1 to about Y15:1. For example, many of the advantages of .the invention are obtained by recycling gases of 4the composition-of the reaction products. This ,can be Vdone by omitting the condensation step, bleeding off to a recovery system a part of the reaction products and recycling the remainder.

Obviously many modifications and variations -of the invention, as hereinbefore set forth, may :be-made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap- .pended claims. f We claim:v Y

' 1. A -process for the production of hydrocarv. bons by the reaction between hydrogen and carbon monoxide which comprises passing into contact with an iron synthesis catalyst at hydrocar- ,bon synthesis temperature and superatmospheric pressure a reactor feed containing hydrogen and carbon monoxide in a mol ratio of at least 15:1.

and comprising one part by volume of fresh feed 12 consisting essentiallyA of hydrogen and carbon monoxide in a mol 'ratio of about 2.5:1 to about 4:1 andabout 8 to about 15 parts by volume of recycled gas, as defined below, separating from theY resulting reaction product the bulk of the C4 and heavier hydrocarbons and oxygenated com- -pounds formed 'in the reaction.' and recycling a portion of'. the remainder of the reaction product as recycled gas for combination with said fresh feed to form said reactor feed.

2. A process for the production of hydrocarbons by the reaction between hydrogen and car- .sure effective to convert at least per cent of the carbon monoxide' contacting said catalyst, sepa.- rating from the resulting reaction product the bulk Vof the C4 and heavier hydrocarbons and oxylgenated compounds formed in the reaction, and

recycling a portion of ,the remainder of the reaction product .as recycled gas for combination with said fresh feed to form said reactor feed.

3. A processl for the production of hydrocarbons by the reaction between hydrogen and carbon monoxide which comprises passing into contact with a fixed bed of an iron synthesis catalyst at least 50 to 100 per cent reduced from the oxide a reactor feed containing hydrogen and carbon monoxide in a mol ratio of about 15:1 to about 30:1 and comprising one part by volume of fresh feed consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 2.8:1 to about 4:1 and about 8 to about 15 parts by volume of recycled gas under conditions including a hydrocarbon synthesis temperature and a superatmospheric pressure effective to convert at least 98 per cent of the carbon monoxide contacting said catalyst, separating from the resulting reaction product the bulk of the C4 and heavier hydrocarbons and oxygenated compounds formed in the reaction, and recycling a portion of the remainder of the reaction product as a recycled gas for combination with said fresh feed to form said reactor feed.

4. A process for the production of hydrocarbons by the reaction between hydrogen and carbon monoxide which comprises passing into contact with a fixed b ed of an iron synthesis catalyst at least partially reduced from the oxide a reactor feed at an elevated reaction initiation temperature, said reactor feed containing hydrogen and carbon monoxide in a mol ratio of about 15:1 t0 about 30: 1 and comprising recycled gas and fresh feed in a volume ratio of about 8:1 to about 15:1, said fresh feed consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 2.8:1 to about 4:1, under conditions effective to convert at least 98 per cent of the carbon monoxide contacting said catalyst, controlling the temperature of the catalyst bed by the temperature of the reactor feed and the volume ratio of recycled gas to fresh feed in the reactor feed, the temperature of the reactor feed and said volume ratio being adjusted so that the temperature gradient across the catalyst bed is between about 100 and about 200 F., separating from the rebon monoxide which comprises passing into contact with a fixed bed of an iron synthesis catalyst at least 50 to 100 per cent reduced from the oxide a reactor feed at an elevated reaction initiation temperature between about 430 and about 475 F., said reactor feed containing hydrogen and carbon monoxide in a mol ratio of about :1 to about 30: 1 and comprising recycled gas and fresh feed in a volume ratio of about 8:1 to about 15:1, said fresh feed consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 28:1, to about 4:1, under conditions effective to convert at least 98 per cent of the carbon monoxide contacting said catalyst, maintaining a temperature gradient across said catalyst bed between about 125 and about 165 F. and a maximum catalyst bed temperature of about 600 to about 630 F., separating from the resulting reaction product the bulk of the C4 and heavier hydrocarbons and oxygenated compounds formed in the reaction, and recycling a portion of the remainder of the reaction product as recycled gas for combination with said fresh feed to form said reactor feed.

6. In a process for the production of hydrocarbons by the reaction between hydrogen and carbon monoxide, the improvement which comprises passing a combination of one part by v01- ume of fresh feed consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 2.8:1 to about 4:1 and about 8 to about 15 parts by volume of a fraction of 'products produced in the reaction into contact with an iron synthesis catalyst at a hydrocarbon synthesis temperature and superatmospheric pressure, said combination of said fresh feed and said fraction containing hydrogen and carbon monoxide in a mol ratio of about 15:1 to about 30:1.

7. A process in accordance with `claim 6 in which said iron synthesis catalyst is at least partially reduced from the oxide.

8. A process in accordance with claim 6 in which said iron synthesis catalyst is 50 to 100 per cent reduced from the oxide.

9. A process for the production of hydrocarbons by the reaction between hydrogen and car` bon monoxide which comprises passing into contact with a fixed bed of an iron synthesis catalyst at least partially reduced from the oxide a reactor feed at an elevated reaction initiation temperature, said reactor feed containing hydrogen and carbon monoxide in a mol ratio of about 15: 1 to about 30:1 and comprising reaction vapors as described below and fresh feed in a volume ratio of about 8:1 to about 15:1, said fresh feed .consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 2.8:1 to about 4:1. under adiabatic -conditions effective to convert at least 98 per cent of the carbon monoxide contacting said catalyst, controlling the temperature of the catalyst bed by the temperature of the reactor feed and the volume ratio of said reaction vapors to fresh feed in the reactor feed, the temperature of the reactor feed and said 14 volume ratio being adjusted so that the temperature gradient across the catalyst bed is between about 100 and 200 F., cooling resulting reaction product to form a condensed fraction and reaction vapors, and recycling at least a portion of said reaction vapors for combination with said fresh feed to form said reactor feed.

10. A process for the production of hydrocarbons by the reaction between hydrogen and carbon monoxide which comprises passing into contact with a xed bed of an iron synthesis catalyst at hydrocarbon synthesis temperature, superatmospheric pressure, and under adiabatic conditions, a reactor feed containing hydrogen and carbon monoxide in a mol ratio of about 15:1 to about 30: 1 and comprising one part by volume of fresh feed consisting essentially of hydrogen and4 carbon monoxide in a mol ratio of about 2.5:1 to about 4:1 and about 8 to about 15 parts 'by volume of reaction vapors as described below, cooling resulting reaction product to form a condensed fraction and reaction vapors, and recycling at least a portion of said reaction vapors for combination with said fresh feed to form said reactor feed.

11. A process for the production of hydrocarbons by the reaction between hydrogen and carbon monoxide which comprises passing into contact with a fixed bed of an iron synthesis catalyst a reactor feed containing hydrogen and carbon monoxide in a mol ratio of about 15:1 to about 30: 1 and comprising one part by volume of fresh feed consisting essentially of hydrogen and carbon monoxide in a mol ratio of about 2.5:1 to about 4:1 and about 8 to about 15 parts by volume of reaction vapors as described below, said contact of said reactor feed with said fixed bed of said catalyst being carried out at hydrocarbon synthesis temperature, superatmospheric pressure and under adiabatic conditions effective to convert at least 98 per cent of the carbon monoxide contacting said catalyst, cooling resulting reaction rproduct to form a condensed fraction and reaction vapors, and recycling at least a portion of said reaction vapors for combination with said fresh feed to form said reactor feed.

CHARLES W. MONTGOMERY. WILLIAM A. HORNE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 943,627 Elworthy Dec. 14, 1909 1,643,663 Klatte Sept. 27, 1927 1,820,417 Williams Aug. 25, 1931 1,999,388 Bader et al Apr. 30, 1935 2,074,311 Moore Mar. 16, 1937 2,251,554 Sabel Aug. 5, 1941 2,271,259 Herbert Jan. 27, 1942 2,461,570 Roberts Feb. 15, 1949 2,481,089 Dickinson Sept. 6, 1949 FOREIGN PATENTS Number Country Date 503,622 Great Britain Apr. 12, 1939 616,499 Great Britain Jan. 21, 1949 OTHER REFERENCES Weil et al., Synthetic Petroleum from the Synthene Process (pages 47 and 88). 

1. A PROCESS FOR THE PRODUCTION OF HYDROCARBONS BY THE REACTION BETWEEN HYDROGEN AND CARBON MONOXIDE WHICH COMPRISES PASSING INTO CONTACT WITH AN IRON SYNTHESIS CATALYST AT HYDROCARBON SYNTHESIS TEMPERATUE AND SUPERATMOSPHERIC PRESSURE A REACTOR FEED CONTAINING HYDROGEN AND CARBON MONOXIDE IN A MOL RATIO OF AT LEAST 15:1 AND COMPRISING ONE PART BY VOLUME OF FRESH FEED CONSISTING ESSENTIALLY OF HYDROGEN AND CARBON MONOXIDE IN A MOL RATIO OF ABOUT 2.5:1 TO ABOUT 4:1 AND ABOUT 8 TO ABOUT 15 PARTS BY VOLUME OF RECYCLED GAS, AS DEFINED BELOW, SEPARATING FROM THE RESULTING REACTION PRODUCT THE BULK OF THE C4 AND HEAVIER HYDROCARBONS AND OXYGENATED COMPOUNDS FORMED IN THE REACTION, AND RECYCLING A PORTION OF THE REMAINDER OF THE REACTION PRODUCT AS RECYCLED GAS FOR COMBINATION WITH SAID FRESH FEED TO FORM SAID REACTOR FEED. 